1. Field of the Invention
The invention relates to a vehicle controller.
2. Description of Related Art
A variety of vehicle controllers have been suggested that automatically stop the engine and enable the economic running operation under predetermined operation conditions of the vehicle. In the economic running operation, the supply of fuel is stopped and therefore fuel consumption can be reduced.
An engine controller according to the related art that enables such economic running operation is described, for example, in Japanese Patent Application Publication No. 2006-200370 (JP-A-2006-200370). The engine automatic stop/start controller described in JP-A-2006-200370 can automatically start the engine when the negative pressure value of a brake booster using the intake negative pressure of the engine as a negative pressure source decreases in the automatic stop state of the engine, and increases the revolution speed and automatically starts the engine when the predetermined condition is fulfilled. More specifically, when the driver has tried to brake abruptly or has operated abruptly the steering wheel, and when the road has changed from a flat road to a sloped road, the revolution speed is increased and the engine is automatically started.
When a brake booster to which the intake negative pressure of the engine is supplied is installed on a vehicle, where the engine is stopped and the vehicle runs in the economic running mode, the negative pressure of the brake booster decreases. Accordingly, after the engine has been restarted, the brake operation performed by the driver cannot be sufficiently assisted by the brake booster and a feeling of uneasiness can be created. In the engine automatic stop/start device according to the above-described related art, when a brake operation is performed such that a large booster negative pressure is consumed in the stopping state of the engine, that is, when an abrupt brake operation is performed, abrupt steering operation is performed, or the vehicle runs on a sloped road, the determination value of engine automatic start is changed, the revolution speed is raised, the engine is automatically started, and the booster negative pressure is rapidly restored.
In the engine automatic stop/start device according to the above-described related art, when the engine is stopped and the vehicle runs in the economic running mode, sufficient negative pressure control of the brake booster is enabled when the driver performs a variety of operations. However, where the vehicle reaches a sloped road and the vehicle speed rises, the driver applies a large brake force or performs pumping braking. Where the booster negative pressure is not sufficient in such cases, the driver's braking operation cannot be sufficiently assisted. Further, in the engine automatic stop/start device according to the above-described related art, although the booster negative pressure is controlled when the vehicle runs on a sloped road, the sloped road should be defined, that is, the gradient angle of the road surface should be set and the control becomes difficult.